How 600 mg of D-Chiro-Inositol May Reduce Oestradiol in Older Men: A Review of the 2021 Nordio Study

Oestrogen balance in men is increasingly recognised as an important component of male health.  While testosterone often takes centre stage, elevated oestrogen—particularly oestradiol—can contribute to symptoms such as fatigue, reduced libido, weight gain, mood changes, and even gynecomastia.  Understanding nutritional and metabolic approaches to supporting oestrogen balance is an emerging area in functional medicine.

One of the most intriguing studies in this space was published in 2021 by Nordio and colleagues (Basic and Clinical Andrology).  This pilot clinical trial investigated whether 600 mg of D-Chiro-Inositol (DCI) daily could influence sex hormones in older hypogonadal men with low-normal testosterone. A key outcome was the effect on oestradiol levels.

What Did the Study Find?

DCI is a naturally occurring compound closely involved in insulin signalling and metabolic regulation.  In the study:

• Men received 600 mg of D-Chiro-Inositol per day over a defined treatment period.

• Researchers measured changes in a range of sex hormones, including oestradiol.

• Notably, participants experienced significant reductions in oestradiol levels after supplementation.

• This was accompanied by improvements in the overall testosterone:estradiol balance—an important factor in male hormone equilibrium.

These findings are particularly relevant because oestradiol is not only present in women; in men, it’s produced via aromatisation of testosterone and plays both physiological and, at times, pathophysiological roles.  Elevated oestradiol in older males has been associated with unwanted symptoms and metabolic disruptions.  A nutritional strategy that supports healthier oestradiol levels could therefore be clinically useful.

Why It Matters

This study suggests that D-Chiro-Inositol may help modulate oestrogen in men—potentially offering a dietary/nutraceutical approach to supporting hormone balance.  While this was a pilot trial with a relatively small sample size, the results provide a foundation for larger research and offer early insights that clinicians and patients alike can explore further.

Importantly, hormone balance is multifactorial.  Diet, exercise, insulin sensitivity, body composition, nutrient status, and aromatase activity all contribute to how oestradiol and testosterone are regulated . DCI’s effects may connect to its influence on insulin signalling, which is known to interact with sex hormone metabolism.

Want More Evidence-Based Insights?

If you’re interested in a deeper look at how dietary factors and specific nutrients influence oestrogen dominance in males, you’ll find a comprehensive review here:

https://doi.org/10.1016/j.hnm.2025.200354

This resource explores current evidence on foods, supplements, and lifestyle factors that may support oestrogen balance in men.